Present systems for magnetic recording on flexible disks require a platform on which a rotating disk can be supported. A disk rotating near a stationary plate interacts with it in such a manner that if a source of air flow is provided at the disk's axis, an attractive force is created between them. This Bernoulli coupling force between disk and plate provides the means for repetitively and effectively positioning the rotating disk relative to the stationary plate. Positioning is achieved because of a balance of inertial, internal, external and fluid dynamic stresses created at the plate-disk interface (PDI). As a result of this balance of stresses, a plate-to-disk separation S=S (R, W, Q, V) is established which is a function of various system parameters, including R=disk radial coordinate, W=rotational frequency, Q=air source flow rate and V=fluid kinematic viscosity.
In a flexible disk non-contact recording system, a recording head or transducer is required to protrude into the plane of the disk in order to achieve transducer-disk spacings which permit digital recording at desired high bit densities. Such protrusions create local instabilities in the PDI, which in turn affects the head-to-disk spacing. The head preferably incorporates a ring stabilizer device such as described and claimed in U.S. Pat. No. 4,003,091, assigned to the same assignee as the present application, which through its fluid dynamic interaction with the rotating disk, acts to pull the disk into its vicinity, and also acts to damp out PDI instabilities which would have been created had the disk-stabilizer effects not been present. In such a Bernoulli-type recording system, the transducer remains spaced from the disk surface, unlike other flexible disk recorders in which the transducer is in contact with the disk surface.
In previous Bernoulli-type recording devices, it has been necessary to employ flat Bernoulli plates made to relatively close tolerances, such as .+-.0.0015 inches, in order to obtain satisfactory performances. This requirement for such close tolerances on flatness understandably increases the cost of manufacturing the devices and makes such devices less attractive, particularly since these devices are intended primarily as low cost products.